Trihydroxydiphenyl as an additive for foundry green molding sands

ABSTRACT

Tridydroxydiphenyl is useful as an additive for improving the properties of foundry green molding sands or clays. The trihydroxydiphenyl is incorporated into the sand in the form of an aqueous solution. Alternatively, the solution may be applied to the surface of a green sand mold for use as a facing agent.

United States Patent 1191 Melcher June 11, 1974 TRIHYDROXYDIPHENYL AS ANADDITIVE [56] References Cited Inventor: Ronald Melcher, o NJ. 2,753,3127/1956 Miller .1 260/172 Assignee: Whitehead Brothers p y, 3,232,7712/1966 Pearce [CG/38.35

Florham Park, NJ. Primary Examiner-Lorenzo B. Hayes 1221 Flled: 1 1972Attorney, Agent, or Firm--Kenyon & Kenyon Reilly 211 Appl. No.: 285,277Carr & Chapm Related us. Application Data [63] Continuation-impart ofSer. No. 28964, April 15, [57] ABSTRACT 1970. abandoned.Tridydroxydiphenyl is useful as an additive for improving the propertiesof foundry green molding sands US. Cl 106/3855, l 6/38.6, or clays. Thetrihydroxydiphenyl is incorporated into 260/DIG- 40 the sand in the formof an aqueous solution. Alterna- [51] Int. Cl B281) 7/34 tively, thesolution may be applied to the surface of a [58] Field Of Search106/383, 38.35, 38.6, green nd mold for use as a facing agent,

106/68; 260/DIG. 40, 37 R 15 Claims, 2 Drawing Figures 2-5 s' as PsmewrH MSM/SS/On 6 8 1 4-5 5 6.5 6 6-57 758 9 IO]! I2 14/6 1TRIHYDROXYDIPHENYL AS AN ADDITIVE FOR FOUNDRY GREEN MOLDING SANDS Thepresent invention relates to additives for foundry green molding sand.More particularly, this invention is concerned with the use oftrihydroxydiphenyl as an additive for foundry green molding sand.

As is well known, the foundry art is that art dealing with the formationof metal articles by casting processes wherein molten metal is pouredinto a mold, allowed to cool, and solidify. By far the largest quantityof castings are made by processes in which the mold is formed from sand,i.e., by sand casting processes. There are several different sandcasting processes, but the one employed most often is that employinggreen molding sand.

Green molding sand has been defined as a plastic mixture of sand grains,clay, water and other materials which can be used for molding andcasting processes. The sand is called greenbecause of the moisturepresent and is thus distinguished from dry sand. (Heine et al.,Principles of Metal Casting, McGraw-l-lill Book Co., lnc., New York(1955), p. 22). Green sand has also been defined as a a naturally bondedsand or a compounded molding-sand mixture which has been tempered withwater for use while still in the damp or wet condition. (Molding Methodsand Materials, lst Ed., The American Foundrymens Society, Des Plaines1962). As employed herein, the term foundry green molding sand" hasreference to green molding sands of the type known to and employed bythose of ordinary skill in the foundry art comprising molding sand andclay and tempered with water. I

As is evident from the foregoing, the essential components of a foundrygreen molding sand are molding sand, clay and water. The molding sand,which usually is a silica sand(e.g., quartz), but which may be a zircon,olivine or other refractory particulate material having mesh sizescommonly in the range of from about 6 to about 270 mesh, serves largelyas a filler and provides the body of the mold. The clay, which is afinely divided (normally less than about 2 microns) material such asmontmorillonite, (bentonite), illite, kaolinite and the like, whenplasticized with water, serves as a binder for the sand grains, andimparts the physical strength necessary to enable use of the greenmolding sand as a mold material. Ordinarily, green molding sands containfrom about 5 to about 20 weight percent clay, based upon sand, andsufficient water, normally not greater than about 6 weight percent,based upon sand, to achieve the desired plasticity and other physicalproperties.

There are a number of properties which are desired in foundry greenmolding sands. Among the most important are:

1. Good flowability or compactibility to allow the sand to move againstthe pattern under compacting forces;

2. Good physical strength after compaction to permit the mold to retainits shape after removal of the pattern and during casting;

3. Dimensional stability during the casting process; 4. Good internalcohesion of the sand grains and poor adhesion of the sand grains to thecast article; and

5. Good collapsibility after casting to facilitate shakeout. There are,of course, subsidiary properties which are related to these properties,including compressive strength, permeability, compactibility, moldhardness,

' green shear, deformation, peel, and the like. In general,

a green molding sand typically has properties within the followingranges:

Green Compression Strength 4 psi Green Shear Strength 0.5 10 psiDeformation 0.005 0.04 in/in Permeability 6.5 400 Dry CompressionStrength 50 200* psi If the deformation is too low, the green moldingsand is too brittle and cannot withstand handling and pattern removal,while if the deformation is too-high dimensional accuracy cannot bemaintained, and the mold,

nology. If permeability is less than 6.5, the vapors generated duringcasting cannot dissipate rapidly enough,

and the mold can rupture from gas pressure and molten metal can beejected out of the sprues. If, on the other I hand, the permeability istoo high, the molten metal V will not be retained in the mold cavity,but will penetra'te the voids of the sand. Finally, if the dry strengthis too low the sand cannot withstand the erosive effect of the flowingmolten metal during casting, while if the dry strength is too high thecasting may crack upon solidification.

ln general, foundry green molding sands consisting solely of sand, clayand water do not possess an optimum balance of properties. For thisreason, a variety of additives have been employed in an effort toimprove the properties of green molding sands. Typically these additivesare organic materials which are used as facing agents, expansion controlagents and the like. In most cases these organic additives are useful inimproving only one property of they green sand and thus two or moreadditives may be required. In addition, an additive employed to improveone property frequently has an adverseeffect on another property of thegreen sand mold.. For example, sea coal or bituminous coal has been usedas a facing agent, and while it does prevent bum-on, it has been foundthat increased amounts of clay and water are necessary to restoredesirable physicalproperties possessed bythe unmodified green sand.

The use of such organic additives is further limited because the totalamount of materials which form gaseous materials under the elevatedtemperatures encountered during casting (i.e., water and organicadditives) must be kept below about 10 weight percent, based upon sand.Excessive amounts of organic materials lead to the generation of moregas than can be dissipated by permeation through the mold body, andwould lead to the failure of the mold and the generation of defects inthe casting. Normally, the loss of weight on ignition due that anaqueous solution of trihydroxydiphenyl is useful as an additive forfoundry green molding sands. More importantly, it has been found that anaqueous solution of trihydroxydiphenyl is unique as a foundry greenmolding sand additive in that it has a beneficial effect ganic additiveto green molding sand, regardless of the casting being made.

In particular, the use of aqueous trihydroxydiphenyl in accordance withthis invention affords the following advantages:

l. The molding sand has good flowability. Thusthe sand is readily formedand compacted around mold patterns of complicated design. Moreover, thesand can be readily employed in automatic molding machines. In addition,the good flowability permits achievement of a desired sand hardness andapparent bulk density with the expenditure of less compacting energythan other green molding sands. Further, the danger of overramming aportion of the mold due to variations in compacting energy is reduceddue to more uniform compaction of the sand. Thus the rammed sand is morehomogeneous with respect to density and therefore strength. I

2. The compacted sand possesses desirable green strength characteristicsat lower moisture contents than are achieved with conventional greenmolding sands.

3. The additive acts as a facing agent, and prevents burn-on or thefusing of quartz sand grains to the surface of the casting, and promotesexcellent finish and peel.

4. The additive reduces shifting of the sand during the casting process,whether it be mold wall movement or enlargement of the mold cavity, orwhether it be a locallized shifting of the sand resulting in suchcasting defects as rat-tails, scabs and buckles.

5. The additive permits casting to be effected at lower pouringtemperatures and promotes increased fluidity of the metal duringcasting.

6. The additive yields adequate dry compression strength and yetexcellent shakeout is obtained even with green molding sands employingWestern bentonite as the clay binder.

'7. Finally, the additive is employed at relatively low levels, which inturn minimizes the formation of gas during casting. 1

Without wishing to be bound by theory, it is believed that the superiorutility of the additive ,of this invention is due, in large part, to thehygroscopic nature of trihydroxydiphenyl, for it is this property whichenables the use of green molding sands having reduced moisture content.As noted above, green molding sands normally contain up to about 6weight percent and typically from about 3 to about 6 weight percentwater. When the moisture content of the conventional sands is less thanabout 3 weight percent, e.g. is 2 weight percent, the waterevaporatesout so rapidly that the sand does not have a useful workinglife, and at moisture contents of 1 weight percent the sand is notcohesive and cannot be formed into a mold. The trihydroxydiphenyl, onthe other hand, because it is hygroscopic, acts as a humectant, andenables the green molding sand to retain its moisture content atmoisture levels as low as 1 weight percent or even less. Indeed, thehygroscopic properties of the resins are so pronounced that the sand canbe retempered without the mulling heretofore required. For example, whendry, particulate RM 441 is allowed to stand at C. and 80 percentrelative hu-' midity it picks up about 53 percent of its own weight ofwater. Thus, retempering can be effected by allowing the molding sand tostand in an atmosphere having a high, e. g., at least about 80 percent,relative humidity. Alternatively, water can be sprinkled on the sand andallowed to equilibrate after'only a minimal degree of mixing orprocessing effort and time. it is also believed that thetrihydroxydiphenyl, like the water, is a plasticizer for the claybinder, and it is this property which enables the formulation of acohesive green molding sand at low moisture contents, eg 1 weightpercent.

The reduced water content of the green molding sand is believedresponsible for a number of advantages. First, less total gas isgenerated during the casting cycle. The reduction in the amount of gasproduced decreases, the amount venting or permeability necessary toallow the gas to escape. As a consequence, sands having higher A.'F.S.fineness numbers can be used, thus providing a better casting finish.Secondly, the reduced amounts of water result in the virutal absence ofa condensation zone or zone of high moisture content resulting fromwater vapor transported from the heated mold surface, in the mold massduring the casting cycle. The absence of this zone elminates defects,such as rat-tails, buckles and scabs normally associated with separationof the dry crust at the mold surfacefrom the body of the mold due to theweaker bond strength in the condensation zone.

The reduced amounts of water in the mold body permits the use of lowerpouring temperatures during casting, since the metal will not be chilledas much through loss of heat to vaporize the water. As a corrolary tothis, the molten metal can flow into thinner and more complexpassageswithout the need for the more elevated temperatures required by currentpractice. Thus the use of trihydroxydiphenyl contributes to improvedmetal fluidity and reduces misruns or cold shut.

The reduced amount of water also tends to reduce the degree of burn-onand-provides better facing action. lt is known that the water present ingreen sand molds, when heated to casting temperature, provides anoxidizing atmosphere which contributes to burn-on. This contribution isminimized by reducing the water content of the sand.

The reduced amount of water also reduces pinhold porosity of thecasting. lt is known that water will decompose m its constituentelements, hydrogen and oxygen, at casting temperatures. The hydrogenthus formed can dissolve in the molten metal, causing gas defectsknownas pinhole porosity. These defects are reduced when the amount of waterin the green sand mold is reduced.

Finally, the reduced moisture content of the sand is believedresponsible for improved shakeout, especially when Western bentonite isemployed as the clay binder. It is known'that the dry compressionstrength developed with green molding sands employing Western bentoniteincreases with increasing moisture content of the green sand. Since areduced moisture content is feasible with applicants invention, reduceddry strengths and thus improved shakeout result.

The trihydroxydiphenyl has other properties which contribute to itsdesirability as a green molding sand additive. Thus, on pyrolysis, thetrihydroxydiphenyl forms a fine, honeycomb, coke-like structure which,it is believed, tends to lock up" the sand grains with a bond inaddition to that afforded by the clay. This bond further retardsshifting of the sand grains and, in particular, is believed responsivefor limiting mold wall movement and cavity enlargement. ln addition, thetrihydroxydiphenyl, like other carbonaceous materials, forms anon-oxidizing atmosphere at casting temperatures, which contributes toits facing activity.

Still another desirable property of trihydroxydiphenyl is its apparentability, in combination with the clay binder, to impart lubricity to thesand grains comprising the green sand, and to permit them to slide pastone another prior to compaction. lt is this property which is believedresponsible for the good flowability of the uncompacted green moldingsand, as well as the ability of the sand to be compacted to highapparent bulk densities with the expenditure of reduced compactingenergy. Moreover, the increased flowability reduces the criticality ofvariations in compacting energy over the mold, and renders the sand lesssusceptible to expansion defects caused by non-uniform ramming of themold. As a result, excellent molds can be made even by less skilledmolders. Despite the good flowability of the uncompacted sand, thetrihydroxydiphenyl imparts a strong cohesion of the sand grains of thecompacted sand. Generally the cohesion is higher than that of theadhesion of the sand to the metal, thus rendering parting agentsunnecessary. Thus, fine details are not lost.

Regardless of the mechanism of its mode of action, however,trihydroxydiphenyl has proven to be a unique additive for foundry greenmolding sands, and is responsible for the improvement of a great numberof the properties of the molding sand. As a result, no other organicadditive need be employed. Moreover, the aqueous trihydroxydiphenyl canbe employed as a substitute for so-called waterless additives, such asthe known bentone-based oleophilic materials. Unlike these materials,whose utility is limited to casting aluminum and light metals, theaqueous trihydroxydiphenyl can be employed for casting all types ofmetals.

Ahtough trihydroxydiphenyl has been found by this invention to be usefulas a foundry green molding sand additive, and it can be employed as suchin pure form if desired, such use is presently uneconomical. It has beenfurther found, however, that crude forms of trihydroxydiphenyl can beemployed satisfactorily. A suitable form of crude trihydroxydiphenyl isthe solid resinous material as a still residue remaining after thedistil-' lation of technical grade resorcinol. Residues of this type, aswell as the recovery of 2,3,4- trihydroxydiphenyl from them, have beendescribed by William E. St. Clair in U.S. Pat. No. 3,133,033 issued May12, 1964 and by William H. Voris in U.S. Pat. No. 3,347,884 issued Oct.17, 1971, as comprising 55 percent trihydroxydiphenyls, plus minoramounts of resorcinol, dihydroxydiphenyl and monohydroxydiphenyls, withthe chief ingredient being 2,3,4- trihydroxydiphenyl. A resinousmaterial of this type is commercially available from Koppers Companyunder the trade designation RM 441.

RM 441 has been described by Paul G. Gemeinhardt in U.S. Pat. No.3,330,781 issued on July 11, 1967, and by Loren J. Miller in U.S. Pat.No. 2,753,312 issued July 3, 1956 as follows: I

RM 441 is a designation given by Koppers Company to a solid resinousmaterial, which is obtained by them as a residue remaining in the stillafter removing technical grade resorcinol as a distillate. A typicalultimate chemical analysis of this material (the percentages given beingby weight) is as follows:

Physically, RM 441 is a drak brown, brittle material having thefollowing characteristics:

Ball and ring softening point, C. to 88 Water solubility, percent 20 to25 lsopropyl alcohol solubility, percent 94 to 98% If technical graderesorcinol is heated at about 200C, there is produced a darkcoloredmaterial appearing and responding similarly to all the testsabove given as "to RM 441. Thus, RM 441 is believed to consistessentially of a condensation product (or mixture thereof) derived fromresorcinol under the influence of heat. It is also known, due to itsorigin, that RM 441 in its present commercialform contains relativelysmall amounts of impurities normally occurring incident to thecommercial manufacture of technical grade resorcinol, for example, smallor trace amounts of 3 mercapto phenol (C H OHSH).

RM 441 can be distilled at low pressure to give about 55 percent of ayellow oily distillate, which will partially crystallize. The crystalsamount to about 60 percent of the distillate (33 percent of the originalRM 441), and melt at about l36C. These crystals, when analyzedcorrectly, are found to be trihydroxydiphenyl the positions of thehydroxyl groups on the two rings being unknown. The oilyportion of thedistillate, representing about 22 percent of the entire RM 441, alsocontains trihydroxydiphenyl, again with the positions of the hydroxylgroups unknown. There is also identified in this oily portion smallportions of dihydroxydiphenyl, again with the positions of the hydroxylgroups unknown. The balance of the RM 441 has not been fully orpositively identified, but is believed to contain further condensationproducts of resorcinol, similar in some respects to thetrihydroxydiphenylabove referred to, and including compounds havingaplurality, probably three or more, phenyl groups linked in eitherstraight or branched chains and with some -Ol-l groups thereon. Thismaterial is believed to be created by the polymerizing or couplingaction of heat upon -resorcinol, eliminating water, probably similar to'a linkage formed between two resorcinol molecules as follows:

momma-wallowin resulting in the chaining together, in either straight orbranched chains or both, of a number of the original resorcinolmolecules. It is further believed that in most instances there is atleast one Ol-l group remaining on each of the phenyl rings, althoughthis has not been identified. Furthermore, in an end group of a chain,it seems likely that there are two hydroxyl groups remaining on thering. For example, a compound of the kind visualized could be expressedby the formula:

Again, in this group of compounds, which is assumed to be reasonablyrepresentative of a substantial portion of the RM 441 the positions ofthe several remaining OH groups are unknown. It is believed that RM 441or a material substantially equivalent and which should for the purposesof the present application be considered as RM 441, is also fonned whenpure resorcinol is heated to 200C., probably due to one or moremolecules of water splitting off, leaving in each instance a phenol ringdeficient in hydrogemthen the phenol molecular deficiency is subject toattachment to another ring as well as with resorcinolper se in order toblance the molecules.

' While there is herein included not only specific technical data whichhas been exactly obtainedas to the characteristics of RM 441, there isalso included all that is presently known of this material. It will beunderstood that any theory expressed therein in'this connection is givenfor what it may be worth, and is not to be considered as specificallylimiting upon the definition of the material, but that any materialderived from the sources above set forth and/or having physical andchemical characteristics generally similar to that particularlydescribed for RM 441,.is to be considered as RM 441 for the purposes ofthis application, including the claims appended hereto.

It will further be understood that inasmuch as RM 441 is obtainedcommercially as a still residue, and as the distillation operation bywhich it is produced may be a batch operation, the composition maydiffer somewhat from time to time.

RM 441 may be briefly defined as a solid resinous material comprising aresidue remaining in the still after removing technical grade resorcinolas a distillate.

Contrary to the above teaching that RM 441 is soluble in water onlyinamounts of up to about 25 percent,

it now has been found that aqueous solutions contain: ing up to about 99parts of RM 441 per part water can be prepared. Indeed, the aqueoussolution characteristics of RM 441 appear to be much more complex thanimplied by the above-quoted reference. Specifically, when RM 441 andwater are mixed in proportions of less than about 0.25 to about 0.35parts resin per part water, there is obtained a milky suspension which,after standing for a few minutes, forms a water-insoluble, black tarryresidue comprising about 8-10 percent of the product and which containsabout 18 to 19 weight percent water. The residue will redissolve onincreasing the solids content to above about 25 percent, and atproportions of RM 441 to water above from about 0.25 to about 0.35 partsresin per part water there is formed a two-phase system comprising aminor amount (generally not more than about 1.2 weight percent of thetotal) of a solid'dispersed in a clear, dark red or brown, slightlyacidic solution having a composition substantially equal to that of thetotal composition. For example, if 2 parts of resin are admixed with 1part of water there is obtained a mixture comprising about 0.03 parts ofsolid and the balance a solution of about 2 partsof solute in 1 part ofwater having a pH-of about 5.2. Because the density of the solid isclose to that of the liquid phase, especially at higher ratios of resinto water,

it does not readily settle but it can be isolated through techniquessuch as filtration or centrifugation. The

pure solid is a white, crystalline material, and when admixed with anequal amount of water, dissolves upon heating to a temperature of atleast about 59F. This solid can also be dissolved by making the aqueouscomposition alkaline (pH greater than 7), as by the addition of ammoniaor an alkali metal hydroxide, e.g., lithium, sodium or potassiumhydroxide.

The aqueous solutions are prepared by any convenient technique, butpreferably by adding heated water to F. to particulate resin having aparticle size of not greater than about 2 inches in the desiredproportions. The resulting mixture is then stirred to promotedissolution and base may be added if desired. It is not necessary thatthe solution be free of any undissolved solid, although the solid can beremoved if desired.

it has been further found that distillation fractions of RM 441 areuseful in accordance with this invention. For example, aqueous solutionsof the abovementioned only distillate and the residue resultingtherefrom are useful in accordance with this invention. However,solutions of the distillate are somewhat less active and solutions ofthe residue are somewhat more active than solutions of the resin RM 441for the applications discussed below.

The distillate, if added to water in a weight ratio'in excess of 121,forms a solution, especially on heating, and the solution can bedilutedwithout forming a precipitate. If, however, the initial solution isallowed to stand for one or two days, crystallization occurs and, upondilution, a pearlescent precipitate forms which can be redissolved bythe addition of base as described above or upon heating. It is to benoted that the aqueous solutions of this invention includes those whichare free of suspended matter, such as the alkaline or heated solutionsmentioned above as well as solutions including the insoluble solid.

The similarity of RM 441 to pure trihydroxydiphenyl is evidenced by thesimilarity of their infrared spectra as set forth in FIGS. 1 and 2, ofwhich FIG. 1 is the spectrum for 98 percent pure 2,3,4-trihydroxydiphenyl and FIG 2 is the spectrum for RM 441.

Although RM 441 is the only acceptable source of crudetrihydroxydiphenyl presently known to applicant to be available on -acommercial basis, it is contemplated by this invention that similarresinous materials containing a substantial proportion (i.e., at least50 weight percent trihydroxydiphenyl) may likewise be employed withoutdeparting from the spirit of this invention. Accordingly, as employedherein, trihydroxydiphenyl has reference to the pure compound as well asto resinous compositions containing a substantial proportion of thehydroxydiphenyl.

It is essential 'to this invention that the trihydroxydiphenyl beemployed in the form of an aqueous solution, for the additive alone isof little or no practical use as afoundry green molding sand additive.It is believed that the water performs a function over and above that ofa mere diluent, and that the plasticizing action of the solution isgreater than that of the trihydroxydiphenyl .or water separately.

The amount of trihydroxydiphenyl in the aqueous solution can varywidely, and generally will be in the range of from about 0.1 part toabout 10 parts per part of water. However, the advantage of low watercontent in the foundry green molding sand is not achieved unless theaqueous composition contains at least about 0.5 parts trihydroxydiphenylper part water, and preferably at least about 1 part per part water.Moreover, concentrations in excess of about 5 parts trihydroxydiphenylper part water ordinarily are too viscous to permit ready distributionthroughout the sand. A ratio in the range of from about 1 to about 2parts trihydroxydiphenyl per part water is preferred. A solution ofequal parts trihydroxydiphenyl and water is especially preferred, sincegreen molding sands made employing more concentrated solutions tend tocreep, especially in large mold masses (i.e., 100 pounds or more).

Higher green strength and shear values are obtained in the green moldingsand when the solution also contains a water soluble hydroxide inamounts of up to about 25 percent, based upon the weight of the resin.Alkali metal hydroxides, especially sodium hydroxide, are preferred,although ammonium hydroxide is also useful. Preferred amounts are in therange of from about 1 to about weight percent, more preferably fromabout 5 to about 10 weight'percent.

Although it is in principle possible to blend dry trihydroxydiphenylwith sand and clay and then add water, thereby forming the solution insitu, it has been found that as a practical matter the solution must beformed and then admixed with the sand, clay and, if necessary,additional temper water. When dry hydroxydiphenyl is blended with thesand and clay and water is subsequently added, long delays, generally 12to 24 hours, are encountered before the clay is plasticized and usefulgreen strength is developed. In contrast, when an aqueous solution isadmixed with sand andclay, plasticization occurs within 5 minutes andthus the sand is ready for use upon mixing. The amount of solution addedto the sand is not critical, provided it is present in an amountsufficient to impart the desired property, be it cohesion, facingactivity, tempering, plasticity or the like. Normally this amount willbe less than about 5 parts per 100 parts sand withfrom about 1 to about3 parts being most usual.

The solution is admixed with the sand and clay in any suitable manner.The temperature of the solution is not critical provided the solution issufficiently fluid to be easily dispersed throughout the sand or clay.For example, a composition composed of 2 parts RM 441 and 1 part watermay be used at a temperature within the range of from about 32F. toabout 120F.

The additive can be mixed directly with a natural or synthetic moldingsand, or it can be added in combination with other additives, such asclay binders of the bentonite, ilite or kaolinitic type. In this regard,it has been found that the additive acts as an activator and plasticizerfor clays of this type, and these compositions are able to develop highgreen strength with the attendant advantage of low water contentimparted by the clay binder. Thus a molding sand including both theadditive of this invention and a clay binder has extremely desirableproperties. i

Although the trihydroxydiphenyl solution is most commonly admixed withthe sand prior to forming the green sand mold, it is also useful as aface dressing or facing agent and can beapplied to the mold surfaceafter the mold has been formed.

The solution may be applied to the mold surface by any convenienttechnique, as by brushing or spraying, with spraying being preferred.When spraying is employed, airless spray techniques are preferred tominimize the incidence of air-entrained particles. The solution diffusesinto the sand at the mold surface without leaving a residueat thesurface. Thus there is no loss of detail, such as is encountered withcommonly employed surface sprays or washes containing fine particles ofan inorganic refractory material.

The concentration of the trihydroxydiphenyl is not critical, providedthe solution has a consistency which pennits its application to the moldsurface and yet contains sufficient resin to permit application of thedesired amount to the surface without requiring excessive amounts ofsolution. In general, however, amounts of trihydroxydiphenyl varyingfrom about 0.35 to about 3 parts per part water have been foundsatisfactory for application as a spray.

The following examples are illustrative. All parts and percentagesare byweight unless otherwise specified.

EXAMPLE 1 Molding sand compositions containing 400 parts Ottawa A.F.S.Testing Sand, 24 parts anhydrous clay and either 12 parts of a 2:1solution of RM 441 in water or 12 parts water as a control were made up.Those containing water only were prepared by mulling clay and sand for 5minutes, adding water and mulling for 10 minutes, whereas thosecontaining RM 441 solution were prepared by mulling sand plus solutionfor 5 minutes, adding the clay and mulling for 10 minutes. Comparativetesting was performed on compositions employing either WesternBentonite, Southern Bentonite, Cedar Heights fire clay or Bondrite BondKaolinitic Clay as the clay, and the molding sand compositions wereevaluated for percent moisture, green compressive strength, green shearstrength and green deformation. The data are summarized in tabular formas follows:

Table l A Physical Properties of Molding Sands Green Green GreenDeforcompr. shear mation, Compositions Moisture str.,psi str.,psi in/in.

W. Bentonite Clay Test 0.8 9.2 3.7 Control 3.0 8.7 2.4 0.23

S. Bentonite Cla lest 0.72 10.2 3.7 Control 2.4 10.0 2.6 0.030

Cedar Heights clay Test 0.7 4.0 1.2 0.025 Control 2.6 2.8 0.6 0.02l

Bondrite Clay Test 0.72 5 3 1.6 0.022 Control 2 6 3 5 0.8 0.02l

" Plastic deformation.

It is readily apparent that the molding sand test compositionsincorporating the aqueous RM 441 were su: 'perior to their correspondingcontrols in green physical properties, despite the presence of less than1 percent water in the molding sand.

EXAMPLE 2 Molding sand compositions composed of 100 parts AFS 80 sand, 5parts Western Bentonite and 2.5 parts of a 2:1 solution of RM 441 inwater were employed under commercial casting conditions to make castingsof gray iron, Navy M and 85-5-5 copper based alloys and aluminum. 1n allinstances the castings were free from rat-tails, buckles and scabsand-exhibited improved surface smoothness, reduced casting weight(generally 3.0 to 4.5 percent less), and closer conformity to patternsize when compared with castings made employing conventional moldingsandcompositions. Similarly superior results were obtained employing aformulation composed of 100 parts AFS 130 sand, 6 parts WesternBentonite and 3 parts of a 2:1 resin RM 441/water solution.

EXAMPLE 3 A test sand containinga 2:1 solution of RM 441 in water and acontrol-sand were used to make iron castings at 2, 700F. using 50percent new iron ingot and 50 percent remelt iron. The pattern employedconsisted of a polystyrene cylinder having a length of about 8 3/16inches and a diameter of about 2.5 inches and one end thereof sealed offwith an aluminum disc having mounted thereon an aluminum cube having0.995-inch square sides. The molds were made up so that the parting linewas at the juncture of the cylinder and the disc, with the cube beingbelow the parting line in the'drag.

The test sand comprised 200 parts New Jersey A.F.S. 130 Fineness Sand, 6parts of the resin solution and 12 parts of Western Bentonite retemperedwith about 1 percent water to provide amixture having a moisture contentof 1.2 percent. After ramming, the mold hardness around the drag edge ofthe pattern was 7882. After casting, the cube portion was measured todetermine its dimensions from the centers of its opposing sides and fromthe centers of its opposed top edges. The side-to-side shrinkage of thecube was 0.007 inch and 0.01 1 inch, or slightly less than the normalshrinkage of 1 inch of iron (0.013 inch), and the edge-to-edge shrinkagewas 0.004 inches in one direction and zero in the other.

The control sand was composed of 200 parts New Jersey A.F.S. 130Fineness Sand, 6 parts Southern Ben- I tonite, 6 parts Western Bentoniteand 7 parts water. The mold hardness around the drag edge of the patternwas 78 to 85. Measurements of the cube showed a sideto-side gain of0.008 inches, and an edge-to-edge gain of 0.020 inches in one directionand 0.025 inches in the other.

After making allowance for the natural shrinkage of iron, one cancompute the extent of mold wall movements. For example, using theside-to-side dimensional shrinkage from the pattern dimension of 0.007inches, the mold wall movement would be 0.013 less 0.007 or 0.006 inch.The calculated mold wall movements are summarized as follows:

Table 11 Mold Wall Movement inches Sand Composition side-to-sideedge-to-edge Test 0.002; 0.006 0.009; 0.013 Control 0.021 0.033; 0.038

It is readily apparent that there was little or no mold wall movementwhen the resin solution of this invention was employed in the sand,whereas there was considerable mold wall movement in its absence.

EXAMPLE 4 EXAMPLE 5 Employing a sand composed of parts New Jersey A.F.S.Fineness Sand, 3 parts Southern Bentonite, 3 parts Western Bentonite and3.5 parts water, a 2- cavity mold was prepared to make two stepcastings,

each having a rectangular drag surface measuring 4 inches by 12 inches,a cope surface provided with three steps measuring 4 inches by 4 inches,and thicknesses of one-half inch, one inch and 2 inches. One cavity wassprayed with a solution of 2 parts of RM 441 in 1 part of water and theother with a solution of equal parts molasses. and water commonly usedas a mold surface dressing agent. Casting was with grey iron (50 percentnew iron) at 2640F., and shake out was after 45 minutes. The castingmade in the cavity sprayed with the RM 441 solution had a light bum-onon some of the drag surface, and the sides had somewhat heavier burnon,while the tops of the steps were perfectly clean. In comparison, thecasting from the cavity sprayed with molasses had severe burn-on on allsurfaces.

EXAMPLE 6 Employing an 8.5-inch by 8.5-inch by 0.5-inch plate as apattern, a mold was made of a composition containing 100 parts NewJersey A.F.S. Fineness Sand, 3 parts Southern Bentonite, 3 parts WesternBentonite and 3.5 parts water, and provided with two gates at one of thecavity surface adjacent the other gate was sprayed withTop Bond, acommercially available top dressing. The mold was cast at 2750F. usingabout 60 percent new iron and the casting was removed after about 1hour. All of the sand in the path of themetal on the surface sprayedwithTop Bond washed away,

while about 25 percent of the sand on the side sprayed with RM 441remained in place in the path of the metal. Thus the RM 441 proved to bea superior top dressing. The surface of the casting corresponding to themold surface which was not sprayed exhibited sematerial being a darkbrown, brittle material having a ball and ring softening point of 80C.to 88C. and an isopropyl alcohol solubility of 94 percent to 98%percent, the proportions of water and the said resinous maaqueoussolution of a solid resinous material comprising a residue remaining inthe still after removing technical grade resorcinol as a distillate,said solid resinous vere burn-on. 5 terial in said aqueous solution andthe amount of said EXAMPLE 7 solution in said molding sand beingsufiicient to impart A series of solutions of equal parts RM 441 and asol-, lmpl'qved greer} sand propajmes to sfild composlhtlonj vent wereprepared. Each of the solutions was then em- P according to clalm 6wherem i l d to prepare a ldi d composition i solution contains fromabout 1 to about 2 parts of said ing 1,500 parts of dry No. 24 sand, 90parts of anhyl0 resinous materlal P P 1 Water; drous bentonite and 45parts of the solution. Each of 8. A composition according to claim 6wherein said the resulting compositions .were evaluated for moisturesolution contains about equal parts of said resinous macontent, theweight of a 2-inch specimen, green comterial and water. pressionstrength, green shear strength, green deforma- 9. A foundry molding sandaccording to claim 8 contion and mold hardness. 'The results of theseexperil taining up to about 5 parts of said solution per 100 ments aresummarized as follows: parts of sand.

Sand Composition Property I o I Deforrn- Hard- Moisture Weight Compr.Shear mation, ness Solvent gm str.psi str.psi in/in psi Propylene 0.06140 2.1 0.6 w 70 glycol Triethylene 0.06 145.5 1.66 0.57 62 glycolMethyl ethyl 0.06 150.7 1.22 0.47 0.0240 66 ketone n-Hexanol 0.06 154.80.65 0.37 0.0188 58 Glycerine 0.06 139.0 2.36 0.74 w 69 Furfuryl alcohol0.06 146.0 1.96 0.63 0.0325 70 lsopropanol 0.06 152.0 1.01 0.35 0.023663.5 Acetone 0.06 141 2.67 0.84 0.0365 72 Diethylamino 0.06 152 1.230.42 0.0247 64.6

propylamine Ethylene glycol 0.03 139 2.90 0.93 71 Water 1.10 147 6.461.66 0.0185 82 Sand dried rapidly, becoming friable.

From the foregoing data, it is evident that only the 1 foundry moldingSand according to claim 8 aqueous solution of RM 441 provided a sandcomposicontaining from about 1 to about 3 parts of said solutioncombining high compression strength, shear tion per 100 parts of saidsand. strength and hardness and low deformation. 11. A foundry moldingsand according to claim 8 What is claimed is: 1 wherein said aqueoussolution contains up to about 1. In a foundry green molding sandcomposition com- 0.25 parts of a dissolved, water-soluble hydroxide perprising molding sand, clay and water, the improvement part of saidresinous material. comprising trihydroxydiphenyl in the form of asolution 4 12. A foundry molding sand according to claim 11 oftrihydroxydiphenyl dissolved in water uniformly ad- 5 wherein saidhydroxide is an alkali metal hydroxide. mixed with said composition, theconcentration of 13. A foundry molding sand according to claim 12trihydroxydiphenyl in said solution and in said compowherein saidaqueous solution contains from about s1tion being sufficient to impartimproved green sand 0,01 t ab ut 0 15 a ts f s di hydroxide per partproperties to said composition. of said resinous material.

. 2. A composrtlon according to claim 1 containing up 14. In a foundrygreen molding sand composltion to about 5 parts of said solution per 100parts of moldcomprising molding sand, clay and water, the improveingsand. ment comprising from about 0.35 parts to about 99 3. A compositionaccording to claim 1 containing parts of a solid resinous materialcomprising a residue from about 1 to about 3 parts of said solution per100 remaining in the still after removing technical grade parts ofmolding sand. resorcinol as a distillate, said solid resinous material4. A composition according to claim 1 wherein said being a dark brown,brittle material having a ball and solution contains from about 1 toabout 2 parts of trihyrlng f ening pomt of 80C to 88C. and an isopropyldroxydiphenyl per part of water. alcohol solub111ty of 94 percent to 98%percent and 1 5. A composition according to claim 4 wherein said P rt OfWater, id aqueous solution being present in an solution contains aboutequal parts of trihydroxydipheamount suf ficlent t0 lrnpart lmprovedgreen sand propd water ertres to said composition.

6.1n a foundry green molding sand composition com- A 1 1 0911 a rding toclaim 14 wherein prising molding sand, clay and water, the improvementSaid q p 9 comprises from about t0 comprising m ldi sa d if r ly ad i dith an about 5 parts of said resinous material per part of water and upto about 0.25 parts of a dissolved, water-soluble hydroxide per part ofsaid resinous material.

2. A composition according to claim 1 containing up to about 5 parts ofsaid solution per 100 parts of molding sand.
 3. A composition accordingto claim 1 containing from about 1 to about 3 parts of said solution per100 parts of molding sand.
 4. A composition according to claim 1 whereinsaid solution contains from about 1 to about 2 parts oftrihydroxydiphenyl per part of water.
 5. A composition according toclaim 4 wherein said solution contains about equal parts oftrihydroxydiphenyl and water.
 6. In a foundry green molding sandcomposition comprising molding sand, clay and water, the improvementcomprising molding sand uniformly admixed with an aqueous solution of asolid resinous material comprising a residue remaining in the stillafter removing technical grade resorcinol as a distillate, said solidresinous material being a dark brown, brittle material having a ball andring softening point of 80*C. to 88*C. and an isopropyl alcoholsolubility of 94 percent to 98 1/2 percent, the proportions of water andthe said resinous material in said aqueous solution and the amount ofsaid solution in said molding sand being sufficient to impart improvedgreen sand properties to said composition.
 7. A composition according toclaim 6 wherein said solution contains from about 1 to about 2 parts ofsaid resinous material per part of water.
 8. A composition according toclaim 6 wherein said solution contains about equal parts of saidresinous material and water.
 9. A foundry molding sand according toclaim 8 containing up to about 5 parts of said solution per 100 parts ofsand.
 10. A foundry molding sand according to claim 8 containing fromabout 1 to about 3 parts of said solution per 100 parts of said sand.11. A foundry molding sand according to claim 8 wherein said aqueoussolution contains up to about 0.25 parts of a dissolved, water-solublehydroxide per part of said resinous material.
 12. A foundry molding sandaccording to claim 11 wherein said hydroxide is an alkali metalhydroxide.
 13. A foundry molding sand according to claim 12 wherein saidaqueous solution contains from about 0.01 to about 0.15 parts of sodiumhydroxide per part of said resinous material.
 14. In a foundry greenmolding sand composition comprising molding sand, clay and water, theimprovement comprising from about 0.35 parts to about 99 parts of asolid resinous material comprising a residue remaining in the stillafter removing technical grade resorcinol as a distillate, said solidresinous material being a dark brown, brittle material having a ball andring softening point of 80*C. to 88*C. and an isopropyl alcoholsolubility of 94 percent to 98 1/2 percent and 1 part of water, saidaqueous solution being present in an amount sufficient to impartimproved green sand properties to said composition.
 15. A compositionaccording to claim 14 wherein said aqueous solution comprises from about0.5 to about 5 parts of said resinous material per part of water and upto about 0.25 parts of a dissolved, water-soluble hydroxide per part ofsaid resinous material.